Organic electrolytic solution and lithium battery employing the same

Abstract

An organic electrolytic solution includes a lithium salt; an organic solvent including a high dielectric constant solvent and a low boiling point solvent; and an additive of a hetero ring compound including a cyano group and an alkenyl group as substituents. The organic electrolytic solution and the lithium battery employing the organic electrolytic solution suppress the reduction decomposition of a polar solvent to improve the capacity retention ratio of the battery. Thus, the charge/discharge efficiency and lifespan of the battery can be improved.

What is claimed is: 
     
       1. An organic electrolytic solution comprising:
 a lithium salt; 
 an organic solvent comprising a high dielectric constant solvent and a low boiling point solvent; and 
 a compound represented by formula (1): 
 
       
         
           
           
               
               
           
         
       
       where X is oxygen or sulfur; each of n and m is independently an integer from 1 to 3; R 1 , R 2 , R 3  and R 4  are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group having from 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having from 1 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to 20 carbon atoms, a substituted or unsubstituted aryl group having from 6 to 30 carbon atoms, a substituted or unsubstituted aryloxy group having from 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having from 2 to 30 carbon atoms, and a substituted or unsubstituted heteroaryloxy group having from 2 to 30 carbon atoms. 
     
     
       2. The organic electrolytic solution of  claim 1 , wherein the compound represented by formula (1) is a compound represented by formula (2): 
       
         
           
           
               
               
           
         
       
       where, X, n, R 1 , R 2 , R 3  and R 4  are defined as in  claim 1 . 
     
     
       3. The organic electrolytic solution of  claim 1 , wherein the compound represented by formula (1) is a compound represented by formula (3): 
       
         
           
           
               
               
           
         
       
       where X, R 1 , R 2 , R 3  and R 4  are defined as in  claim 1 . 
     
     
       4. The organic electrolytic solution of  claim 1 , wherein the compound represented by formula (1) is a compound represented by formula (4): 
       
         
           
           
               
               
           
         
       
       where R 1  and R 2  are as defined as in  claim 1 . 
     
     
       5. The organic electrolytic solution of  claim 1 , wherein the compound represented by formula (1) is a compound represented by formula (5): 
       
         
           
           
               
               
           
         
       
     
     
       6. The organic electrolytic solution of  claim 1 , wherein the amount of the compound of formula (1) is from 0.1 to 5% by weight based on the weight of the organic solvent. 
     
     
       7. The organic electrolytic solution of  claim 1 , wherein the amount of the compound of formula (1) is from 1 to 3% by weight based on the weight of the organic solvent. 
     
     
       8. The organic electrolytic solution of  claim 1 , wherein the concentration of the lithium salt is from 0.5 to 2.0 M. 
     
     
       9. The organic electrolytic solution of  claim 1 , wherein the high dielectric constant solvent includes at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyrolactone. 
     
     
       10. The organic electrolytic solution of  claim 1 , wherein the low boiling point solvent includes at least one solvent selected from the group consisting of dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, dipropyl carbonate, dimethoxyethane, diethoxyethane, and a fatty acid ester derivative. 
     
     
       11. A lithium battery comprising: a cathode; an anode; and an organic electrolytic solution comprising: a high dielectric constant solvent and a low boiling point solvent; and a compound represented by formula (1): 
       
         
           
           
               
               
           
         
       
       where X is oxygen or sulfur; each of n and m is independently an integer from 1 to 3; R 1 , R 2 , R 3  and R 4  are each independently selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, a substituted or unsubstituted alkyl group having from 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having from 1 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to 20 carbon atoms, a substituted or unsubstituted aryl group having from 6 to 30 carbon atoms, a substituted or unsubstituted aryloxy group having from 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having from 2 to 30 carbon atoms, and a substituted or unsubstituted heteroaryloxy group having from 2 to 30 carbon atoms. 
     
     
       12. The lithium battery of  claim 11 , wherein the compound represented by formula (1) is a compound represented by formula (2): 
       
         
           
           
               
               
           
         
       
       where, X, n, R 1 , R 2 , R 3  and R 4  are defined as in  claim 11 . 
     
     
       13. The lithium battery of  claim 11 , wherein the compound represented by formula (1) is a compound represented by formula (3): 
       
         
           
           
               
               
           
         
       
       where X, R 1 , R 2 , R 3  and R 4  are defined as in  claim 11 . 
     
     
       14. The lithium battery of  claim 11 , wherein the compound represented by formula (1) is a compound represented by formula (4): 
       
         
           
           
               
               
           
         
       
       where R 1  and R 2  are as defined as in  claim 11 . 
     
     
       15. The lithium battery of  claim 11 , wherein the compound represented by formula (1) is a compound represented by formula (5): 
       
         
           
           
               
               
           
         
       
     
     
       16. The lithium battery of  claim 11 , wherein the amount of the compound of formula (1) is from 0.1 to 5% by weight based on the weight of the organic solvent. 
     
     
       17. The lithium battery of  claim 11 , wherein the amount of the compound of formula (1) is from 1 to 3% by weight based on the weight of the organic solvent. 
     
     
       18. The lithium battery of  claim 11 , wherein the concentration of the lithium salt is from 0.5 to 2.0 M. 
     
     
       19. The lithium battery of  claim 11 , wherein the high dielectric constant solvent includes at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, and γ-butyrolactone. 
     
     
       20. The lithium battery of  claim 11 , wherein the low boiling point solvent includes at least one solvent selected from the group consisting of dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, dipropyl carbonate, dimethoxyethane, diethoxyethane, and a fatty acid ester derivative.